Microbial inhibiting compositions and their use

ABSTRACT

A biocidal composition and method for inhibiting and controlling the growth of the fungus, Trichoderma viride, are disclosed. The composition comprises an amount, effective for the intended purpose of diiodomethyl-p-tolylsulfone and an additional biocidal component. The method comprises administering between about 0.1 to about 200 parts of this combined treatment (based on one million parts of the desired aqueous system) to the particular water containing system for which treatment is desired.

BACKGROUND OF THE INVENTION

The present invention relates to methods for controlling the growth ofmicrobes in an aqueous system. More particularly, it relates to methodsof microbial inhibition which entail adding to the system compositionscomprising diiodomethyl-p-tolylsulfone (DIMPS) and at least one othercomponent, the composition exhibiting synergy.

The formation of slimes by microorganisms is a problem that isencountered in many aqueous systems. For example, the problem is notonly found in natural waters such as lagoons, lakes, ponds, etc., andconfined waters as in pools, but also in such industrial systems ascooling water systems, air washer systems and pulp and paper millsystems. All possess conditions which are conducive to the growth andreproduction of slime-forming microorganisms. In both once-through andrecirculating cooling systems, for example, which employ largequantities of water as a cooling medium, the formation of slime bymicroorganisms is an extensive and constant problem.

Airborne organisms are readily entrained in the water from coolingtowers and find this warm medium an ideal environment for growth andmultiplication. Aerobic and heliotropic organisms flourish on the towerproper while other organisms colonize and grow in such areas as thetower sump and the piping and passages of the cooling system. The slimeformation not only aids in the deterioration of the tower structure inthe case of wooden towers, but also promotes corrosion when it depositson metal surfaces. Slime carried through the cooling system plugs andfouls lines, valves, strainers, etc., and deposits on heat exchangesurfaces. In the latter case, the impedance of heat transfer can greatlyreduce the efficiency of the cooling system.

In pulp and paper mill systems, slime formed by microorganisms iscommonly encountered and causes fouling, plugging, or corrosion of thesystem. The slime also becomes entrained in the paper produced to causebreakouts on the paper machines, which results in work stoppages and theloss of production time. The slime is also responsible for unsightlyblemishes in the final product, which result in rejects and wastedoutput.

The previously discussed problems have resulted in the extensiveutilization of biocides in cooling water and pulp and paper millsystems. Materials which have enjoyed widespread use in suchapplications include chlorine, chlorinated phenols, organs-bromines, andvarious organo-sulfur compounds. All of these compounds are generallyuseful for this purpose but each is attended by a variety ofimpediments. For example, chlorination is limited both by its specifictoxicity for slime-forming organisms at economic levels and by thetendency of chlorine to react, which results in the expenditure of thechlorine before its full biocidal function is achieved.

Other biocides are attended by odor problems and hazards with respect tostorage, use or handling which limit their utility. To date, no onecompound or type of compound has achieved a clearly establishedpredominance with respect to the applications discussed. Likewise,lagoons, ponds, lakes, and even pools, either used for pleasure purposesor used for industrial purposes for the disposal and storage ofindustrial wastes, become, during the warm weather, besieged by slimedue to microorganism growth and reproduction. In the case of industrialstorage or disposal of industrial materials, the microorganisms causeadditional problems which must be eliminated prior to the use of thematerials or disposal of the waste.

Naturally, economy is a major consideration with respect to all of thesebiocides. Such economic considerations attach to both the cost of thebiocide and the expense of its application. The cost performance indexof any biocide is derived from the basic cost of the material, itseffectiveness per unit of weight, the duration of its biocidal orbiostatic effect in the system treated, and the ease and frequency ofits addition to the system treated. To date, none of the commerciallyavailable biocides has exhibited a prolonged biocidal effect. Instead,their effectiveness is rapidly reduced as a result of exposure tophysical conditions such as temperature, association with ingredientscontained by the system toward which they exhibit an affinity orsubstantivity, or the like, with a resultant restriction or eliminationof their biocidal effectiveness, or by dilution.

As a consequence, the use of such biocides involves their continuous orfrequent addition to systems to be treated and their addition tomultiple points or zones in the systems to be treated. Accordingly, thecost of the biocide and the labor cost of applying it are considerable.In other instances, the difficulty of access to the zone in which slimeformation is experienced precludes the effective use of a biocide. Forexample, if in a particular system there is no access to an area atwhich slime formation occurs the biocide can only be applied at a pointwhich is upstream in the flow system. However, the physical or chemicalconditions, e.g., chemical reactivity, thermal degradation, which existbetween the point at which the biocide may be added to the system andthe point at which its biocidal effect is desired render the effectiveuse of a biocide impossible.

Similarly, in a system experiencing relatively slow flow, such as apaper mill, if a biocide is added at the beginning of the system, itsbiocidal effect may be completely dissipated before it has reached allof the points at which this effect is desired or required. As aconsequence, the biocide must be added at multiple points, and even thena diminishing biocidal effect will be experienced between one point ofaddition to the system and the next point downstream at which thebiocides may be added. In addition to the increased cost of utilizingand maintaining multiple feed points, gross ineconomies with respect tothe cost of the biocide are experienced. Specifically, at each point ofaddition, an excess of the biocide is added to the system in order tocompensate for that portion of the biocide which will be expended inreacting with other constituents present in the system or experiencephysical changes which impair its biocidal activity.

It has been found possible to provide a fungicidal or biocidalcomposition which comprises, as active ingredients,diiodomethyl-p-tolylsulfone and at least one additional chemicalcomponent. The additional component may be:

1) 2-bromo-2-nitropropane-1,3-diol (BNPD),

2) sodium 2-pyridinethiol-l-oxide (PEO), or

3) 2-(thiocyano-methyl thio) benzothiazole (TCMTB).

Surprisingly, it has been found that mixtures ofdiiodomethyl-p-tolylsulfone with any of the additional biocidalcomponents listed are especially efficacious in controlling the growthof fungal microbes, specifically the Trichoderma iride species. Thisparticular species is a common nuisance fungal type found in industrialcooling waters and pulping and papermaking systems.

This particular species of mold is a member of the Fungi Imperfectiwhich reproduce by means of asexual spores or fragmentation of mycelium.It is commonly found on fallen timber and is a widely occurring soilorganism. Because of its ubiquitous nature, this mold continuallycontaminates open cooling systems and pulping and papermaking systems.Contamination can take the form of airborne spores or fungal mats--amass of agglomerated hyphae bound together with bacterial cells andcemented by gelatinous polysaccharide or proteinaceous material. Theslimy mass entraps other detritus, restricts water flow and heattransfer and may serve as a site for corrosion.

These fungi are able to grow in environments hostile to other lifeforms.While they are strict aerobes, Trichoderma produce both hyphae, thevegetative structure, and spores which require minimal metabolicturnover and are able to withstand harsher environmental conditions.Accordingly, by reason of demonstrated efficacy in the growth inhibitionof this particular species, one can expect similar growth inhibitionattributes when other fungi are encountered. It is also expected thatthese compositions will exhibit similar growth inhibition attributeswhen bacterial and algal species are encountered.

According to the present invention there is provided a method forcontrolling the growth of fungi, particularly Trichoderma iride fungi,in an aqueous system, which comprises adding to the system from about0.1 to 200 parts by weight of the aqueous system, of a compositioncomprising a synergistic mixture of (a) diiodomethyl-p-tolylsulfone and(b) at least one additional biocidal component selected from (1) to (3)as hereinbefore defined. The aqueous system may comprise, for example, acooling water system or a pulping and papermaking system.

In accordance with the present invention, the combined treatment ofdiiodomethyl-p-tolylsulfone with any one of the additional biocidalcomponents may be added to the desired aqueous system in need ofbiocidal treatment, in an amount of from about 0.1 to about 200 parts ofthe combined treatment to one million parts (by weight) of the aqueousmedium. Preferably, about 5 to about 50 parts of the combined treatmentper one million parts (by weight) of the aqueous medium is added.

The combined treatments are added, for example, to cooling watersystems, paper and pulp mill systems, pools, ponds, lagoons, or lakes,to control the formation of fungal microorganisms, which may becontained by, or which may become entrained in, the system to betreated. It has been found that the compositions and methods ofutilization of the treatments are efficacious in controlling the fungalorganism, Trichoderma viride which may populate these systems. It isthought that the combined treatment compositions and methods of thepresent invention will also be efficacious in inhibiting and controllingall types of aerobic microorganisms.

Surprisingly, it has been found that when the ingredients are mixed, incertain instances, the resulting mixtures possess a higher degree offungicidal activity than that of the individual ingredients comprisingthe mixtures. Accordingly, it is possible to produce highly efficaciousbiocides. Because of the enhanced activity of the mixtures, the totalquantity of the biocidal treatments may be reduced. In addition, thehigh degree of biocidal effectiveness which is provided by each of theingredients may be exploited without use of higher concentrations ofeach.

The following experimental data were developed. It is to be rememberedthat the following examples are to be regarded solely as beingillustrative, and not as restricting the scope of the invention.

Diiodomethyl-p-tolylsulfone and an additional biocidal component wereadded in varying ratios and over a wide range of concentrations to aliquid nutrient medium which was subsequently inoculated with a standardvolume of a suspension of the spores from Trichoderma viride. Growth wasmeasured by determining the amount of radioactivity accumulated by thecells when 14C-glucose was added as the sole source of carbon in thenutrient medium. The effect of the biocide chemicals, alone and incombination, is to reduce the rate and amount of 14C incorporation intothe cells during incubation, as compared to controls not treated withthe chemicals. Additions of the biocides, alone and in varyingcombinations and concentrations, were made according to the accepted"checkerboard" technique described by M. T. Kelley and J. M. Matsen,Antimicrobial Agents and Chemotherapy. 9: 440 (1976). Following a twohour incubation, the amount of radioactivity incorporated in the cellswas determined by counting (14C liquid scintillation procedures) for alltreated and untreated samples. The percent reduction of each treatedsample was calculated from the relationship: ##EQU1##

Plotting the % reduction of 14C level against the concentration of eachbiocide acting alone results in a dose-response curve, from which thebiocide dose necessary to achieve any given reduction can beinterpolated.

Synergism was determined by the method of calculation described by F. C.Kull, P. C. Eisman, H. D. Sylwestrowicz and R. L. Mayer, AppliedMicrobiology 9,538 (1961) using the relationship: ##EQU2## where: ^(Q)a=quantity of compound A, acting alone, producing an end point

^(Q) b=quantity of compound B, acting alone, producing an end point

^(Q) A=quantity of compound A in mixture, producing an end point

^(Q) B=quantity of compound B in mixture, producing an end point

The end point used in the calculations is the % reduction caused by eachmixture of A and B. ^(Q) A and ^(Q) B are the individual concentrationsin the A/B mixture causing a given % reduction. ^(Q) a and ^(Q) b aredetermined by interpolation from the respective dose-response curves ofA and B as those concentrations of A and B acting alone which producethe same % reduction as each specific mixture produced.

Dose-response curves for each active acting alone were determined bylinear regression analysis of the dose-response data. Data were fittedto a curve represented by the equation shown with each data set. Afterlinearizing the data, the contributions of each biocide component in thebiocide mixtures to the inhibition of radioisotope uptake weredetermined by interpolation with the dose-response curve of therespective biocide. If, for example, quantities of ^(Q) A plus ^(Q) Bare sufficient to give a 50% reduction in 14C content, ^(Q) a and ^(Q) bare those quantities of A or B acting alone, respectively, found to give50% reduction in 14C content. A synergism index (SI) is calculated foreach combination of A and B.

Where the SI is less than 1, synergism exists. Where the SI=1,additivity exists. Where the SI is greater than 1, antagonism exists.The data in the following tables come from treating Trichoderma viride,a common nuisance fungal type found in industrial cooling waters and inpulping and paper making systems, with varying ratios and concentrationsof diiodomethyl-p-tolylsulfone and each additional biocidal component.Shown for each combination is the reduction of 14C content (% 1), thecalculated SI, and the weight ratio of diiodomethyl-p-tolylsulfone andeach additional biocidal component.

                  TABLE I                                                         ______________________________________                                        DIMPS vs. BNPD                                                                ppm       ppm      Ratio                                                      DIMPS.sup.1                                                                             BNPD.sup.2                                                                             DIMPS:BNPD    % I  SI                                      ______________________________________                                        6         0        100:0         88                                           3         0        100:0         76                                           1.5       0        100:0         48                                           0.75      0        100:0         28                                           0.38      0        100:0         20                                           0.19      0        100:0         12                                           0         1200     0:100         80                                           0         600      0:100         73                                           0         300      0:100         60                                           0         150      0:100         42                                           0         75       0:100         29                                           0         37.5     0:100         19                                           6         1200     1:200         92   1.53                                    3         1200     1:400         89   1.27                                    1.5       1200     1:800         76   1.96                                    0.75      1200     1:1600        82   1.26                                    0.38      1200     1:3158        81   1.25                                    0.19      1200     1:6316        49   6.10                                    6         600      1:100         91   1.22                                    3         600      1:200         87   0.95                                    1.5       600      1:400         88   0.94*                                   0.75      600      1:800         77   0.90*                                   0.38      600      1:1600        75   0.92*                                   0.19      600      1:3158        35   6.62                                    6         300      1:50          91   1.06                                    3         300      1:100         85   0.79*                                   1.5       300      1:200         76   0.80*                                   0.75      300      1:400         70   0.78*                                   0.38      300      1:800         66   0.81*                                   0.19      300      1:1600        28   5.05                                    6         1.50     1:25          91   0.97                                    3         150      1:50          86   0.67*                                   1.5       150      1:100         74   0.66*                                   0.75      150      1:200         64   0.68*                                   0.38      150      1:400         82   0.22*                                   0.19      150      1:800         56   0.63*                                   6         75       1:12.5        92   0.91*                                   3         75       1:25          85   0.64*                                   1.5       75       1:50          69   0.67*                                   0.75      75       1:100         52   0.85*                                   0.38      75       1:200         73   0.22*                                   0.19      75       1:400         41   0.78*                                   6         37.5     1:6.25        91   0.92*                                   3         37.5     1:12.5        83   0.65*                                   1.5       37.5     1:25          63   0.80*                                   0.75      37.5     1:50          40   1.17                                    0.38      37.5     1:100         62   0.28*                                   0.19      37.5     1:200         33   0.72*                                   ______________________________________                                         .sup.1 product containing 40% actives DIMPS                                   .sup.2 product containing 95% actives BNPD                               

                  TABLE II                                                        ______________________________________                                        DIMPS vs. BNPD                                                                ppm       ppm      Ratio                                                      DIMPS.sup.1                                                                             BNPD.sup.2                                                                             DIMPS:BNPD    % I  SI                                      ______________________________________                                        6         0        100:0         91                                           3         0        100:0         81                                           1.5       0        100:0         59                                           0.75      0        100:0         26                                           0.38      0        100:0         0                                            0.19      0        100:0         0                                            0         1200     0:100         81                                           0         600      0:100         71                                           0         300      0:100         56                                           0         150      0:100         38                                           0         75       0:100         22                                           0         37.5     0:100         6                                            6         1200     1:200         95   1.72                                    3         1200     1:400         91   1.38                                    1.5       1200     1:800         87   1.24                                    0.75      1200     1:1600        84   1.23                                    0.38      1200     1:3158        82   1.22                                    0.19      1200     1:6316        82   1.48                                    6         600      1:100         94   1.43                                    3         600      1:200         90   1.04                                    1.5       600      1:400         83   0.94*                                   0.75      600      1:800         78   0.89*                                   0.38      600      1:1600        74   0.94*                                   0.19      600      1:3158        72   0.96                                    6         300      1:50          94   1.30                                    3         300      1:100         88   0.89*                                   1.5       300      1:200         79   0.76*                                   0.75      300      1:400         73   0.69*                                   0.38      300      1:800         65   0.76*                                   0.19      300      1:1600        60   0.87*                                   6         150      1:25          93   1.24                                    3         150      1:50          87   0.83*                                   1.5       150      1:100         77   0.66*                                   0.75      150      1:200         67   0.60*                                   0.38      150      1:400         56   0.69*                                   0.19      150      1:800         44   0.93*                                   6         75       1:12.5        94   1.18                                    3         75       1:25          88   0.77*                                   1.5       75       1:50          76   0.59*                                   0.75      75       1:100         59   0.62*                                   0.38      75       1:200         38   0.89*                                   0.19      75       1:400         21   1.39                                    6         37.5     1:6.25        93   1.19                                    3         37.5     1:12.5        86   0.76*                                   1.5       37.5     1:25          73   0.60*                                   0.75      37.5     1:50          48   0.76*                                   0.38      37.5     1:100         22   1.20                                    0.19      37.5     1:200         11   1.32                                    ______________________________________                                         .sup.1 product containing 40% actives DIMPS                                   .sup.2 product containing 95% actives BNPD                               

                  TABLE III                                                       ______________________________________                                        DIMPS vs. PEO                                                                 ppm       ppm      Ratio                                                      DIMPS.sup.1                                                                             PEO.sup.2                                                                              DIMPS:PEO     % I  SI                                      ______________________________________                                        6         0        100:0         85                                           3         0        100:0         77                                           1.5       0        100:0         58                                           0.75      0        100:0         38                                           0.38      0        100:0         29                                           0.19      0        100:0         25                                           0         80,000   0:100         91                                           0         40,000   0:100         86                                           0         20,000   0:100         80                                           0         10,000   0:100         66                                           0          5,000   0:100         48                                           0          2,500   0:100         47                                           6         80,000   1:13,333      92   2.07                                    3         80,000   1:26,666      91   1.79                                    1.5       80,000   1:53,333      91   1.60                                    0.75      80,000   1:106,666     90   1.56                                    0.38      80,000   1:280,701     90   1.52                                    0.19      80,000   1:421,052     90   1.51                                    6         40,000   1:6,666       92   1.44                                    3         40,000   1:13,333      89   1.21                                    1.5       40,000   1:26,666      88   1.11                                    0.75      40,000   1:53,333      86   1.09                                    0.38      40,000   1:105,263     86   1.06                                    0.19      40,000   1:210,526     85   1.04                                    6         20,000   1:3,333       91   1.12                                    3         20,000   1:6,666       89   0.82*                                   1.5       20,000   1:13,333      84   0.84*                                   0.75      20,000   1:26,666      78   0.98                                    0.38      20,000   1:52,631      76   1.13                                    0.19      20,000   1:105,263     72   1.25                                    6         10,000   1:1,666       91   0.98                                    3         10,000   1:3,333       87   0.70*                                   1.5       10,000   1:6,666       82   0.63*                                   0.75      10,000   1:13,333      68   1.10                                    0.38      10,000   1:26,315      61   1.47                                    0.19      10,000   1:52,631      58   1.68                                    6          5,000   1:833         90   0.91*                                   3          5,000   1:1,666       88   0.56*                                   1.5        5,000   1:3,333       81   0.47*                                   0.75       5,000   1:6,666       63   0.97                                    0.38       5,000   1:13,157      53   1.36                                    0.19       5,000   1:26,315      50   1.49                                    6          2,500   1:417         91   0.83*                                   3          2,500   1:833         89   0.49*                                   1.5        2,500   1:1666        82   0.39*                                   0.75       2,500   1:3,333       61   0.74*                                   0.38       2,500   1:6,579       50   1.03                                    0.19       2,500   1:13,158      47   0.97                                    ______________________________________                                         .sup.1 product containing 40% actives DIMPS                                   .sup.2 product containing 40% actives PEO                                

                  TABLE IV                                                        ______________________________________                                        DIMPS vs. PEO                                                                 ppm       ppm      Ratio                                                      DIMPS.sup.1                                                                             PEO.sup.2                                                                              DIMPS:PEO     % I  SI                                      ______________________________________                                        6         0        100:0         81                                           3         0        100:0         71                                           1.5       0        100:0         58                                           0.75      0        100:0         37                                           0.38      0        100:0         19                                           0.19      0        100:0         13                                           0         80,000   0:100         90                                           0         40,000   0:100         86                                           0         20,000   0:100         75                                           0         10,000   0:100         58                                           0          5,000   0:100         48                                           0          2,500   0:100         45                                           6         80,000   1:13,333      94   1.58                                    3         80,000   1:26,666      94   1.30                                    1.5       80,000   1:53,333      93   1.22                                    0.75      80,000   1:106,666     92   1.18                                    0.38      80,000   1:280,701     92   1.12                                    0.19      80,000   1:421,052     92   1.12                                    6         40,000   1:6,666       93   1.19                                    3         40,000   1:13,333      91   0.95*                                   1.5       40,000   1:26,666      90   0.83*                                   0.75      40,000   1:53,333      89   0.77*                                   0.38      40,000   1:105,263     SS   0.74*                                   0.19      40,000   1:210,526     SB   0.75*                                   6         20,000   1:3,333       92   0.95*                                   3         20,000   1:6,666       91   0.66*                                   1.5       20,000   1:13,333      86   0.64*                                   0.75      20,000   1:26,666      82   0.65*                                   0.38      20,000   1:52,631      80   0.66*                                   0.19      20,000   1:105,263     79   0.68*                                   6         10,000   1:1,666       90   0.91*                                   3         10,000   1:3,333       89   0.55*                                   1.5       10,000   1:6,666       81   0.55*                                   0.75      10,000   1:13,333      78   0.50*                                   0.38      10,000   1:26,315      75   0.52*                                   0.19      10,000   1:52,631      64   0.96                                    6          5,000   1:833         90   0.86*                                   3          5,000   1:1,666       87   0.54*                                   1.5        5,000   1:3,333       83   0.38*                                   0.75       5,000   1:6,666       72   0.46*                                   0.38       5,000   1:13,157      65   0.56*                                   0.19       5,000   1:26,315      48   1.39                                    6          2,500   1:417         88   0.86*                                   3          2,500   1:833         87   0.49*                                   1.5        2,500   1:1666        79   0.40*                                   0.75       2,500   1:3,333       62   0.59*                                   0.38       2,500   1:6,579       48   0.96                                    0.19       2,500   1:13,158      46   0.87*                                   ______________________________________                                         .sup.1 product containing 40% actives DIMPS                                   .sup.2 product containing 40% actives PEO                                

                  TABLE V                                                         ______________________________________                                        DIMPS vs. PEO                                                                 ppm       ppm      Ratio                                                      DIMPS.sup.1                                                                             PEO.sup.2                                                                              DIMPS:PEO     % I  SI                                      ______________________________________                                        6         0        100:0         81                                           3         0        100:0         74                                           1.5       0        100:0         55                                           0.75      0        100:0         27                                           0.38      0        100:0          6                                           0.19      0        100:0          0                                           0         80,000   0:100         88                                           0         40,000   0:100         86                                           0         20,000   0:100         77                                           0         10,000   0:100         61                                           0          5,000   0:100         50                                           0          2,500   0:100         43                                           6         80,000   1:13,333      91   2.07                                    3         80,000   1:26,666      90   1.72                                    1.5       80,000   1:53,333      89   1.62                                    0.75      80,000   1:106,666     86   1.71                                    0.38      80,000   1:280,701     88   1.52                                    0.19      80,000   1:421,052     88   1.49                                    6         40,000   1:6,666       89   1.63                                    3         40,000   1:13,333      88   1.22                                    1.5       40,000   1:26,666      85   1.14                                    0.75      40,000   1:53,333      89   0.99                                    0.38      40,000   1:105,263     83   1.07                                    0.19      40,000   1:210,526     83   1.08                                    6         20,000   1:3,333       89   1.31                                    3         20,000   1:6,666       88   0.86*                                   1.5       20,000   1:13,333      83   0.79*                                   0.75      20,000   1:26,666      77   0.91*                                   0.38      20,000   1:52,631      75   0.95*                                   0.19      20,000   1:105,263     73   1.01                                    6         10,000   1:1,666       87   1.21                                    3         10,000   1:3,333       86   0.74*                                   1.5       10,000   1:6,666       82   0.57*                                   0.75      10,000   1:13,333      71   0.77*                                   0.38      10,000   1:26,315      67   0.88*                                   0.19      10,000   1:52,631      65   0.89*                                   6         5,000    1:833         87   1.13                                    3         5,000    1:1,666       86   0.65*                                   1.5       5,000    1:3,333       82   0.44*                                   0.75      5,000    1:6,666       69   0.57*                                   0.38      5,000    1:13,157      61   0.70*                                   0.19      5,000    1:26,315      60   0.65*                                   6         2,500    1:417         87   1.07                                    3         2,500    1:833         85   0.62*                                   1.5       2,500    1:1666        76   0.48*                                   0.75      2,500    1:3,333       59   0.68*                                   0.38      2,500    1:6,579       45   1.11                                    0.19      2,500    1:13,158      45   0.94*                                   ______________________________________                                         .sup.1 product containing 40% actives DIMPS                                   .sup.2 product containing 40% actives PEO                                

                  TABLE VI                                                        ______________________________________                                        DIMPS vs. TCMTB                                                               ppm    ppm        Ratio                                                       DIMPS.sup.1                                                                          TCMTB.sup.2                                                                              DIMPS:TCMTB   % I  SI                                       ______________________________________                                        6      0          100:0         87                                            3      0          100:0         69                                            1.5    0          100:0         41                                            0.75   0          100:0         16                                            0.38   0          100:0          7                                            0.19   0          100:0          3                                            0      30         0:100         91                                            0      15         0:100         87                                            0      7.50       0:100         75                                            0      3.75       0:100         61                                            0      1.87       0:100         46                                            0      0.93       0:100         25                                            6      30         1:5.00        96   1.81                                     3      30         1:10.00       95   1.56                                     1.5    30         1:20.0        93   1.50                                     0.75   30         1:40.0        92   1.51                                     0.38   30         1:78.95       91   1.55                                     0.19   30         1:157.89      91   1.54                                     6      15         1:2.5         93   1.43                                     3      15         1:5.00        91   1.18                                     1.5    15         1:10.0        88   1.09                                     0.75   15         1:20.0        86   1.06                                     0.38   15         1:39.47       86   0.99                                     0.19   15         1:78.95       87   0.94*                                    6      7.50       1:1.25        90   1.23                                     3      7.50       1:2.50        85   1.02                                     1.5    7.50       1:5.00        79   1.00                                     0.75   7.50       1:10.0        76   0.98                                     0.38   7.50       1:19.74       74   0.95*                                    0.19   7.50       1:39.47       75   0.89*                                    6      3.75       1.60:1        89   1.08                                     3      3.75       1:1.25        82   0.85*                                    1.5    3.75       1:2.50        70   0.96                                     0.75   3.75       1:5.00        64   0.99                                     0.38   3.75       1:9.87        62   0.93*                                    0.19   3.75       1:19.74       62   0.88*                                    6      1.87       3.21:1        89   0.98                                     3      1.87       1.60:1        81   0.73*                                    1.5    1.87       1:1.25        62   0.99                                     0.75   1.87       1:2.49        52   1.06                                     0.38   1.87       1:4.92        49   1.00                                     0.19   1.87       1:9.84        43   1.16                                     6      0.93       6.45:1        90   0.90*                                    3      0.93       3.23:1        80   0.67*                                    1.5    0.93       1.61:1        50   1.24                                     0.75   0.93       1:1.24        37   1.42                                     0.38   0.93       1:2.45        30   1.40                                     0.19   0.93       1:4.89        29   1.26                                     ______________________________________                                         .sup.1 product containing 40% actives DIMPS                                   .sup.2 product containing 80% actives TCMTB                              

                  TABLE VII                                                       ______________________________________                                        DIMPS vs. TCMTB                                                               ppm    ppm        Ratio                                                       DIMPS.sup.1                                                                          TCMTB.sup.2                                                                              DIMPS:TCMTB   % I  SI                                       ______________________________________                                        6      0          100:0         87                                            3      0          100:0         77                                            1.5    0          100:0         49                                            0.75   0          100:0         21                                            0.38   0          100:0         5                                             0.19   0          100:0         0                                             0      25         0:100         92                                            0      12.50      0:100         84                                            0      6.25       0:100         73                                            0      3.13       0:100         59                                            0      1.56       0:100         41                                            0      0.78       0:100         21                                            6      25         1:4.17        96   1.92                                     3      25         1:8.33        94   1.63                                     1.5    25         1:16.67       93   1.53                                     0.75   25         1:33.33       92   1.47                                     0.38   25         1:65.79       91   1.48                                     0.19   25         1:131.58      91   1.41                                     6      12.5       1:2.08        93   1.53                                     3      12.5       1:4.17        89   1.27                                     1.5    12.5       1:8.33        86   1.18                                     0.75   12.5       1:16.67       85   1.10                                     0.38   12.5       1:32.90       85   1.02                                     0.19   12.5       1:65.79       85   0.96                                     6      6.25       1:1.04        91   1.33                                     3      6.25       1:2.08        84   1.11                                     1.5    6.25       1:4.17        75   1.19                                     0.75   6.25       1:8.33        74   1.01                                     0.38   6.25       1:16.45       73   0.94*                                    0.19   6.25       1:32.89       75   0.79*                                    6      3.13       1.9:1         89   1.21                                     3      3.13       1:1.04        81   0.95*                                    1.5    3.13       1:2.09        69   1.00                                     0.75   3.13       1:4.17        63   0.98                                     0.38   3.13       1:8.2         63   0.84*                                    0.19   3.13       1:16.47       60   0.86*                                    6      1.56       3.8:1         90   1.10                                     3      1.56       1.9:1         81   0.81*                                    1.5    1.56       1:1.04        62   1.00                                     0.75   1.56       1:2.08        48   1.23                                     0.38   1.56       1:4.10        45   1.10                                     0.19   1.56       1:8.21        36   1.43                                     6      0.78       7.69:1        89   1.07                                     3      0.78       3.85:1        80   0.78*                                    1.5    0.78       1.92:1        59   0.92*                                    0.75   0.78       1:1.04        40   1.22                                     0.38   0.78       1:2.05        32   1.20                                     0.19   0.78       1:4.10        24   1.35                                     ______________________________________                                         .sup.1 Product containing 40% actives DIMPS                                   .sup.2 Product containing 80% actives TCMTB                              

                  TABLE VIII                                                      ______________________________________                                        DIMPS vs. TCMTB                                                               ppm    ppm        Ratio                                                       DIMPS.sup.1                                                                          TCMTB.sup.2                                                                              DIMPS:TCMTB   % I  SI                                       ______________________________________                                        6      0          100:0         88                                            3      0          100:0         65                                            1.5    0          100:0         41                                            0.75   0          100:0         24                                            0.38   0          100:0         12                                            0.19   0          100:0         8                                             0      25         0:100         89                                            0      12.50      0:100         79                                            0      6.25       0:100         60                                            0      3.13       0:100         41                                            0      1.56       0:100         29                                            0      0.78       0:100         17                                            6      25         1:4.17        95   1.43                                     3      25         1:8.33        93   1.24                                     1.5    25         1:16.67       91   1.15                                     0.75   25         1:33.33       90   1.10                                     0.38   25         1:65.79       89   1.10                                     0.19   25         1:131.58      89   1.08                                     6      12.5       1:2.08        92   1.15                                     3      12.5       1:4.17        86   1.05                                     1.5    12.5       1:84733       83   0.96                                     0.75   12.5       1:16.67       81   0.92*                                    0.38   12.5       1:32.90       79   0.90*                                    0.19   12.5       1:65.79       80   0.85*                                    6      6.25       1:1.04        90   1.02                                     3      6.25       1:2.08        79   0.99                                     1.5    6.25       1:4.17        68   1.14                                     0.75   6.25       1:8.33        64   1.10                                     0.38   6.25       1:16.45       60   1.16                                     0.19   6.25       1:32.89       58   1.17                                     6      3.13       1.9:1         90   0.88*                                    3      3.13       1:1.04        76   0.89*                                    1.5    3.13       1:2.09        60   1.15                                     0.75   3.13       1:4.17        52   1.14                                     0.38   3.13       1:8.2         45   1.26                                     0.19   3.13       1:16.47       42   1.31                                     6      1.56       3.8:1         91   0.80*                                    3      1.56       1:0.52        75   0.81*                                    1.5    1.56       1:1.04        50   1.31                                     0.75   1.56       1:2.08        42   1.18                                     0.38   1.56       1:4.10        36   1.18                                     0.19   1.56       1:8.21        32   1.14                                     6      0.78       7.69:1        90   0.79*                                    3      0.78       3.85:1        72   0.85*                                    1.5    0.78       1.92:1        47   1.27                                     0.75   0.78       1:1.04        31   1.46                                     0.38   0.78       1:2.05        24   1.31                                     0.19   0.78       1:4.10        21   1.10                                     ______________________________________                                         .sup.1 Product containing 40% actives DIMPS                                   .sup.2 Product containing 80% actives TCMTB                              

Asterisks in the SI column indicate synergistic combinations inaccordance with the Kull method supra.

In the preceding tables, for all combinations tested, differences seenbetween the replicates are due to normal experimental variance.

In accordance with the preceding tables, unexpected results occurredmore frequently within the following product ratios:

    ______________________________________                                                     From about                                                       ______________________________________                                        DIMPS to BNPD  1:1600 to 1:6.25                                               DIMPS to PEO   1:211,000 to 1:417                                             DIMPS to TCMTB 1:79.0 to 7.69:1                                               ______________________________________                                    

The individual products contain the following amounts of active biocidalcomponents:

DIMPS: about 40%

BNPD: about 95%

TCMTB: about 80%

PEO: about 40%

Therefore, when based on the active biocidal component, unexpectedresults appear more frequently within the following ranges of activecomponents:

    ______________________________________                                                     From about                                                       ______________________________________                                        DIMPS to BNPD  1:3800 to 1:14.8                                               DIMPS to PEO   1:211,000 to 1:417                                             DIMPS to TCMTB  1:158 to 3.85:1                                               ______________________________________                                    

At present, it is most preferred that commercial products embodying theinvention comprise weight ratios of active components of about:

    ______________________________________                                        1:15              DIMPS:BNPD                                                  1:500             DIMPS:PEO                                                   1:1               DIMPS:TCMTB                                                 ______________________________________                                    

While this invention has been described with respect to particularembodiments thereof, it is apparent that numerous other forms andmodifications of this invention will be obvious to those skilled in theart. The appended claims and this invention generally should beconstrued to cover all such obvious forms and modifications which arewithin the true spirit and scope of the present invention.

We claim:
 1. A method for controlling the growth of fungal microbes inan aqueous system which comprises adding to an infected aqueous system asynergistic fungicidally effective amount of the mixture ofdiiodomethyl-p-tolylsulfone and (b) 2-bromo-2-nitropropane-1,3 diol, theweight ratio of (a) to (b) being from about 1:3800 to 1:14.8.
 2. Themethod as recited in claim 1 wherein said composition is added to saidsystem in an amount of from about 0.1 to about 200 parts per million ofsaid aqueous system.
 3. The method as recited in claim 1 wherein theweight ratio of (a) to (b) is about 1:15.
 4. The method as recited inclaim 1 wherein said aqueous system comprises a cooling water system. 5.The method as recited in claim 1 wherein said aqueous system comprises apulping and papermaking system.
 6. The method as recited in claim 1wherein said fungal microbes are of the Trichoderma viride variety.